Lasers, photodetectors, and other optical components are widely used in many optoelectronic applications such as, for example, optical communications systems. Traditionally in such applications, manual positioning and tuning of the components is required to maintain the desired optical coupling between the system components However, such manual positioning can be slow and quite expensive.
More recently, in attempts to eliminate this manual positioning of the system components, small tunable lenses (also known as tunable microlenses) were developed to achieve optimal optical coupling. Typically, these microlenses are placed between an optical signal transmitter, such as a laser, and an optical signal receiver, such as a photodetector. The microlens, which uses a droplet of liquid as a lens, acts to focus the optical signal (e.g., that is emitted by the laser) onto its intended destination (e.g., the photodetector). In some cases the position and curvature of these microlenses is automatically varied in order to change the optical properties (e.g., the focal length and focal spot position) of the microlens when, for example, the direction or divergence of a light beam incident upon the microlens varies from its optimized direction or divergence. Thus, the desired optical coupling is maintained between the components of the optical system. Therefore, the manual positioning and adjustment required in previous systems is either substantially reduced or even completely eliminated.
While the prior art electrowetting-based microlenses described above are useful in certain applications, they are also limited in certain aspects of their usefulness. In particular, none of the prior art electrowetting microlenses provided a mechanism for achieving automatic microlens calibration, i.e. its automatic return to some nominal, calibrated state with a defined position and focal length. This might be disadvantageous in certain applications. For example, there are many situations where some sort of a search and optimization algorithm needs to be employed in order to achieve optimal tuning/positioning of the droplet. In the prior art solutions, which do not use a calibration mechanism to first calibrate the position of the droplet, the algorithm must start from an unknown microlens position. This could result in a substantial increase in the time necessary to complete the microlens tuning/positioning process.